Soil Health Improvement Technologies to Enhance Drought and Nutrient Resilience in Urban Agroecosystems in Zimbabwe

Soil degradation which is linked to poor soil organic matter management remains a significant barrier to sustained crop production in smallholder urban agriculture (UA) in sub-Saharan Africa (SSA). While organic nutrient resources are often used in UA to complement inorganic fertilisers in soil fertility management, they are usually scarce and of poor quality to provide optimum nutrients for crop uptake. Alternative soil nutrient management options are required. Aluminium-water treatment residual (Al-WTR), a by-product of the drinking water treatment process is an alternative organo-mineral resource that can be used to complement mineral and organic nutrient resources in urban agroecosystems. Although previous research has revealed the transformative effects of Al-WTR on soil physicochemical properties, there is still some inconsistency about the effects of Al-WTR on relations between plant yield and nutrients, particularly phosphorus (P). The aim of this study was to evaluate the impact of co-applying Al-WTR in combination with other organic nutrient resources (compost, cattle manure and maize stover) as ‘co-amendments’ on soil physical, biological, and chemical properties, P sorption and maize productivity in UA in Zimbabwe. The study employed field, greenhouse, and laboratory approaches to test different Al-WTR-based options for improved soil health. The main treatments included single amendments of Al-WTR, compost (C), cattle manure (CM), maize stover (MS) or their co-amendments as Al-WTR + CM, Al-WTR + MS or Al-WTR + C; an unamended control and standard NPK. A field experiment to determine the influence of Al-WTR co-amendments on soil organic carbon (SOC) and selected soil physical properties showed higher accumulation of SOC and lower soil bulk density; higher soil structural stability, water holding capacity and higher maize grain yields in the co-amendments compared to the unamended soils. The co-amendment of Al-WTR and cattle manure (Al-WTR + CM) accumulated higher (4.96 g. kg-1) concentration of SOC and the lowest (1.30 g cm-3) bulk density, whilst the unamended control recorded the least (4.55 g. kg-1) in SOC and the highest (1.35 g. cm-3) bulk density. The co-amendment, Al-WTR + CM also exhibited greater soil structural stability, recording an average of 121.64 g. kg-1 water-stable aggregates (WSA) and 0.17 mm in mean weighted diameter (MWD), equating to an increase of 393% (WSA) and 141% (MWD), relative to the unamended control. The co-amendment, Al-WTR + CM also resulted in increments of at least 0.02 cm3 cm-3 in readily available water, whilst also retaining > 10% more water at field capacity relative to the control. Both co-amendments, Al-WTR + CM and Al-WTR and maize stover (Al-WTR + MS) in turn yielded four times more maize grain yield compared to the unamended control. Results also showed a higher biological activity in the co-amendments, suggestive of a high turnover potential of the co-amendments in restoring soil health. The co-amendment of Al-WTR + CM attained the highest microbial biomass carbon (190 ± 1.14 mg C kg-1) and microbial biomass nitrogen (35.80 ± 0.51 mg N kg-1) at 6 weeks after planting maize, whereas the least (120 ± 1.58 mg C kg- 1 and 18.72 ± 0.35 mg N kg-1) were recorded for the unamended control. Soil basal respiration (CO2-C emission) was higher in Al-WTR + MS, which gave the highest CO2-C emission of 167 ± 3.44 mg CO2-C kg-1 soil. The unamended control on the other hand recorded a higher metabolic quotient, releasing > 0.10 mg CO2-C microbial C day-1 more, compared to the co-amendments, suggesting more available carbon in the co-amendments and therefore less microbial strain compared to the unamended soil. Results of a short-term greenhouse experiment to evaluate the benefits of applying Al-WTR in combination with compost and inorganic P fertiliser, on soil chemical properties, and maize (Zea mays L.) productivity and nutrient uptake showed higher (3.92 ± 0.16 g) maize shoot biomass at 5 weeks after emergence in the co-amendment of 10% C + 10% Al-WTR, significantly (p <0.05) out-yielding the unamended control which yielded 1.33 ± 0.17 g. The addition of inorganic P fertiliser to the co-amendment (10% C + 10% Al-WTR + P) further increased maize shoot yield by about six-fold (7.23 ± 0.07 g), showing the important role of inorganic P fertilisers in crop production. The co-amendment, 10% Al-WTR + 10% C + P increased maize uptake of the micronutrients Zinc (Zn), Copper (Cu) and Manganese (Mn) by 13.63-, 1.08- and 0.79- mg kg-1, respectively, compared with the single amendment of 10% C + P. The enhanced micronutrient uptake can potentially improve maize grain quality and subsequently human nutrition for the urban population in SSA. A laboratory experiment to understand P sorption characteristics of a sandy soil co-amended with different ratios of Al-WTR and compost under varying levels of pH, particle size and P concentration showed higher maximum P sorption in the single amendment of Al-WTR compared to the co-amendments. The co-amendments in turn showed a reduction in crop inorganic P fertiliser requirements by ranges of 30 - 70% in the co-amendments compared to the single amendment of Al-WTR. Overall, results from this study showed that Al-WTR co-amendments can be used to re-build soil heath, enhance maize productivity, and improve human nutrition in smallholder urban agro-systems of Southern Africa and partly contribute to the United Nations Sustainable Development Goals (UN SDGs) linked to both soil and human health

Boosting soil literacy in schools can help improve understanding of soil/human health linkages in Generation Z

Soil health underpins ecosystem services like food security and therefore underpins human health. Poor soil health is a global problem which is hindering attempts to deliver the UN’s Sustainable Development Goals. We focus on goals 3 (human health), 13 (climate change) which are intimately linked to goal 15 (soil health). Soil health is arguably most fragile in regions such as sub-Saharan Africa (SSA) where aged soils are characterised by poor nutrient and water holding capacity, and are largely deficient in micronutrients such as Zinc. Poor soil health coupled with the largely cereal-based diets can mean that micronutrient malnutrition is high in the region. In sub-Saharan Africa, where much of the population is too poor to purchase mineral supplements, poor soil health (SDG15) can therefore negatively impact on human health (SDG3). We surveyed 3661 school children aged 13–15 in three African countries, Ghana, South Africa and Zimbabwe, for their ‘Attitudes, Behaviours and Competencies’ of soil, which we termed ‘ABC’. The ‘ABC’ survey results showed significant soil illiteracy. The survey showed that although students were generally equipped with a good attitude to (overall 52% positive) and behaviour towards soil (overall 60% engagement), they had little competency as to how to improve soil health (overall 23% knowledge). For example, less than 35% of respondents across all countries know that soil is living. Less than 13% of students are aware of the important role of soil in climate change mitigation. We believe that these two knowledge gaps must be addressed for Generation Z to understand the important linkages between climate change, soil and human health. We propose a hands-on ‘ethics of care’ approach to engage society with soil, piggybacking on existing climate change educational resources by building terrariums with living soil can empower children to learn about soil, plant, human and planetary health. The future of food security depends on Generation Z having soil literacy. Our survey clearly shows that students who think farming is a good way to make money have significantly higher levels of overall soil literacy. We propose that the future of human health depends on soil literacy

The microbiology of rebuilding soils with water treatment residual co‐amendments: Risks and benefits

Water treatment residuals (WTR) are sludges from the potable water treatment process, currently largely destined for landfill. This waste can be diverted to rebuild degraded soils, aligning with the UN's Sustainable Development Goals 12 (Consumption and Production) and 15 (Terrestrial Ecosystems). Biosolids are tested against stringent pathogen guidelines, yet few studies have explored the microbial risk of WTR land application, despite anthropogenic impacts on water treatment. Here, the microbial risks and benefits of amending nutrient-poor sandy soil with WTR were explored. It was shown that the culturable pathogen load of wet and dry WTR did not warrant pre-processing before land application, according to South African national quality guidelines, with fecal coliforms not exceeding 104 CFU/gdw in wet sludges sampled from four South African and Zimbabwean water treatment plants, and decreasing upon drying and processing. There was no culturable pathogenic (fecal coliforms, enterococci, Salmonella and Shigella) regrowth in soil incubations amended with dry WTR. However, the competition (microbial load and diversity) introduced by a WTR co-amendment did not limit pathogen survival in soils amended with biosolids. The application of WTR to nutrient-poor sandy soils for wheat (Triticum aestivum L.) growth improved the prokaryotic and eukaryotic culturable cell concentrations, similar to compost. However, the compost microbiome more significantly impacted the bacterial beta diversity of the receiving soil than WTR, analyzed with ARISA. Thus, although there was a low pathogen risk for WTR-amendment in receiving soils, and total soil microbial loads were increased, microbial diversity was more significantly enhanced by compost than WTR

Translating integrated soil fertility management information and knowledge into crop productivity benefits through farmer learning and participatory action in Eastern Zimbabwe

Smallholder farmers in Zimbabwe and elsewhere in sub-Saharan Africa are faced with challenges of low crop yields linked to inherently poor soils. Integrated soil fertility management (ISFM) is one of the many technologies that have been developed in response to the challenges of continued decline in soil productivity. However, the knowledge has not been effectively transferred to smallholders who are the end-users of the technology resulting in poor adoption. This study was therefore, carried out to evaluate the effectiveness of participatory knowledge and information management and smallholder farmer learning alliances in ISFM technology dissemination and uptake. The study was conducted under the auspices of the Soil Fertility Consortium for Southern Africa (SOFECSA) which provided a framework for developing agricultural knowledge and information systems in Dendenyore and Goto smallholder farming communities. Mhondoro was co-opted as a control site. Data was obtained through participatory approaches that included formal and informal questionnaire surveys, focus group discussions, farmer meetings, personal observations, field-based farmer experiments and laboratory analyses. Results from detailed exploration of relationships among farmer acquisition, sharing and use patterns of ISFM information and knowledge indicates that > 90% of the farmers relied on national extension as a major source of ISFM information. Field based learning centres (LCs) were the major platform of information and knowledge sharing, accounting for ~50% of all the identified platforms. Uptake of ISFM was influenced by farmer resource group and farmers’ visits to LCs. Farmer experience and access to extension services in turn influenced farmer use of ISFM information. Results suggest the need to continuously capacitate extension in participatory approaches that embrace farmer interactive participation and joint exploration with clients for improved adoption of ISFM technologies. Results further indicated that farmers were able to consistently follow their own locally-derived indicators in the monitoring and evaluation processes for agricultural activities. Farmer criteria for preference of ISFM technologies was underpinned by prospects for multiple benefits, low costs of accessing the technology, gender, resource endowment and knowledge of its use. Those participating in learning alliances, which were further subdivided into (i) lead farmer-led group, (ii) extension worker-led group, and (iii) an independent group without a defined leader, had significantly higher maize grain yields (P extension-led farmer group > independent group > control. In this study, Learning centres were useful as platforms for sharing knowledge and exchange of information, and supported participation of farmers in the evaluation of ISFM technologies providing scope for their adoption. It was concluded that farmers with access to technical information on ISFM and related agricultural technologies stand to benefit more through improvement of soil fertility status of their soils and subsequent crop yield increases. Findings from this study contribute to the knowledge base on opportunities available for improved flow of information on mechanisms that enhance user control in the technology development processes to better sustain household food security and environmental integrity within this millennia.,Regional University Forum (RUFORUM

Presentation1_Boosting soil literacy in schools can help improve understanding of soil/human health linkages in Generation Z.pdf

Soil health underpins ecosystem services like food security and therefore underpins human health. Poor soil health is a global problem which is hindering attempts to deliver the UN’s Sustainable Development Goals. We focus on goals 3 (human health), 13 (climate change) which are intimately linked to goal 15 (soil health). Soil health is arguably most fragile in regions such as sub-Saharan Africa (SSA) where aged soils are characterised by poor nutrient and water holding capacity, and are largely deficient in micronutrients such as Zinc. Poor soil health coupled with the largely cereal-based diets can mean that micronutrient malnutrition is high in the region. In sub-Saharan Africa, where much of the population is too poor to purchase mineral supplements, poor soil health (SDG15) can therefore negatively impact on human health (SDG3). We surveyed 3661 school children aged 13–15 in three African countries, Ghana, South Africa and Zimbabwe, for their ‘Attitudes, Behaviours and Competencies’ of soil, which we termed ‘ABC’. The ‘ABC’ survey results showed significant soil illiteracy. The survey showed that although students were generally equipped with a good attitude to (overall 52% positive) and behaviour towards soil (overall 60% engagement), they had little competency as to how to improve soil health (overall 23% knowledge). For example, less than 35% of respondents across all countries know that soil is living. Less than 13% of students are aware of the important role of soil in climate change mitigation. We believe that these two knowledge gaps must be addressed for Generation Z to understand the important linkages between climate change, soil and human health. We propose a hands-on ‘ethics of care’ approach to engage society with soil, piggybacking on existing climate change educational resources by building terrariums with living soil can empower children to learn about soil, plant, human and planetary health. The future of food security depends on Generation Z having soil literacy. Our survey clearly shows that students who think farming is a good way to make money have significantly higher levels of overall soil literacy. We propose that the future of human health depends on soil literacy.</p

DataSheet1_Boosting soil literacy in schools can help improve understanding of soil/human health linkages in Generation Z.docx

Soil health underpins ecosystem services like food security and therefore underpins human health. Poor soil health is a global problem which is hindering attempts to deliver the UN’s Sustainable Development Goals. We focus on goals 3 (human health), 13 (climate change) which are intimately linked to goal 15 (soil health). Soil health is arguably most fragile in regions such as sub-Saharan Africa (SSA) where aged soils are characterised by poor nutrient and water holding capacity, and are largely deficient in micronutrients such as Zinc. Poor soil health coupled with the largely cereal-based diets can mean that micronutrient malnutrition is high in the region. In sub-Saharan Africa, where much of the population is too poor to purchase mineral supplements, poor soil health (SDG15) can therefore negatively impact on human health (SDG3). We surveyed 3661 school children aged 13–15 in three African countries, Ghana, South Africa and Zimbabwe, for their ‘Attitudes, Behaviours and Competencies’ of soil, which we termed ‘ABC’. The ‘ABC’ survey results showed significant soil illiteracy. The survey showed that although students were generally equipped with a good attitude to (overall 52% positive) and behaviour towards soil (overall 60% engagement), they had little competency as to how to improve soil health (overall 23% knowledge). For example, less than 35% of respondents across all countries know that soil is living. Less than 13% of students are aware of the important role of soil in climate change mitigation. We believe that these two knowledge gaps must be addressed for Generation Z to understand the important linkages between climate change, soil and human health. We propose a hands-on ‘ethics of care’ approach to engage society with soil, piggybacking on existing climate change educational resources by building terrariums with living soil can empower children to learn about soil, plant, human and planetary health. The future of food security depends on Generation Z having soil literacy. Our survey clearly shows that students who think farming is a good way to make money have significantly higher levels of overall soil literacy. We propose that the future of human health depends on soil literacy.</p

Coapplication of water treatment residual and compost for increased phosphorus availability in arable sandy soils

IntroductionSoil degradation coupled with poor access to organic nutrient resources remains a major constraint in increased crop productivity in sub-Saharan Africa, thus hindering the continent's efforts in achieving the United Nations' Sustainable Development Goals, particularly goals 1 (end poverty), 2 (zero hunger) and 3 (improve human health). Water treatment residual (WTR), a by-product of clean water treatment, has been identified as an alternative organic nutrient resource for crop production. However, there are some inconsistences in soil phosphorus (P) dynamics following aluminium WTR (Al-WTR) application.Materials & MethodsA laboratory experiment was conducted to evaluate the P sorption of a sandy soil amended with 10% Al-WTR, 10% compost (C) as a quasi-control, 10% C + 10% Al-WTR (10% coamendment) and 5% C + 5% Al-WTR (5% coamendment) under varying levels of pH, particle size and P concentration. We calculated crop P fertilizer requirements under different amendments.ResultsThe results demonstrated that all amendments exceeded the minimum of 0.2 mg P L−1 needed in soil solution at equilibrium to maintain plant growth. However, the maximum P sorption capacity was higher for 10% Al-WTR single amendment, ranging from 770 to 1000 mg P Kg−1, and from 714 to 1000 mg P Kg−1 and 555 to 909 mg P Kg−1 for 10% and 5% coamendments, respectively, across a range of pH and soil particle size fractions. The coamendments showed a reduction in crop P fertilizer requirements by ranges of 30–60% and 60–70% for the 10% and 5% coamendment levels, respectively, across different pH and particle sizes, relative to 10% Al-WTR.ConclusionResults show that the use of 5% coamendment in sandy soils increases P availability sufficiently to improve crop yields. The results provide scope for using Al-WTR coamendments to rebuild soil health in sandy soils in urban agriculture and increase macronutrient provision in crops to support human health

A nation that rebuilds its soils rebuilds itself- an engineer's perspective

Nations can build and rebuild degraded soils to help address climate change and potentially improve the nutritional content of food if we change policies that allow the addition of safe mineral and organic wastes to soil. We present a framework that facilitates the transition from intensive conventional to more regenerative farming practices by considering soil's natural cycle. Our paper is presented in three parts. Firstly, we consider that 'soil is living'; just like humans, the soil biome needs a balanced diet of macro and micronutrients as well as a nurturing environment. We simplify the soil science and take a systems approach which focuses on restoring soil's natural cycle to benefit both health (by increasing micronutrients in soil) and wealth (through climate change adaptation and mitigation). Secondly, we consider the scale of the problem of soil degradation and the timescales involved in rebuilding soils and barriers to implementation. Thirdly, we propose a potential framework which enables communities to identify what might be missing from soil's natural cycle. This framework helps communities consider how they might change soil texture by addition and manipulation of both minerals and organic matter. We present an educational tool, ‘soil in a jar’ based on a narrative of nurturing soil which is designed to engage and inspire society to get their hands dirty. Communities can use the framework to produce locally specific solutions to restore their soil's natural cycle and rebuild their local and national economies